Radio-frequency identification tag

ABSTRACT

A radio-frequency identification (RFID) tag includes: a plate-shaped sealing piece made of an elastic material. An inlet is enclosed within the sealing piece. The inlet includes an electronic component and an antenna connected to the electronic component. A pair of reinforcing pieces are located respectively on the front and back surfaces of the sealing piece so as to sandwich the electronic component. The reinforcing pieces are made of a first material harder than the elastic material. A joint piece configured to couple the reinforcing pieces to each other. The joint piece is made of a second material harder than the elastic material.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2008-293822 filed on Nov. 17,2008, the entire contents of which are incorporated herein by reference.

FIELD

The embodiments discussed herein are related to a radio-frequencyidentification (RFID) tag.

BACKGROUND

An RFID tag is well known. The RFID tag is attached on clothes, forexample. The RFID tag includes an inlet airtightly enclosed within asealing piece. The sealing piece is made of rubber, for example. Theinlet includes a semiconductor chip. The RFID tag is configured totransmit and receive a predetermined radio signal in accordance with theoperation of the semiconductor chip. A pair of reinforcing pieces isembedded within the sealing piece. The semiconductor chip is interposedbetween the reinforcing pieces. The reinforcing pieces are made ofplastic, for example.

-   Publication 1: JP Patent Application Laid-open No. 61-204788-   Publication 2: JP Patent Application Laid-open No. 2002-366918-   Publication 3: JP Patent Application Laid-open No. 2008-021033-   Publication 4: JP Patent Application Laid-open No. 2005-242723-   Publication 5: JP Patent Application Laid-open No. 2008-046668-   Publication 6: JP Patent Application Laid-open No. 2007-072829-   Publication 7: JP Patent Application Laid-open No. 11-296642-   Publication 8: JP Patent Application Laid-open No. 2006-031089

When the clothes are washed or spin-dried, an RFID tag suffers fromstress as a result of twisting, bending, shrinkage or elongation of theclothes. Bending stress is generated in the sealing piece, for example.The reinforcing pieces are configured to absorb the stress. However,since the reinforcing pieces separately absorb the stress, thereinforcing pieces are not allowed to have a sufficient rigidity.Consequently, if the sealing piece suffers from a relatively largestress, the semiconductor chip can be damaged.

SUMMARY

According to an aspect of the invention, a radio-frequencyidentification tag including: a plate-shaped sealing piece made of anelastic material; an inlet enclosed within the sealing piece, the inletincluding an electronic component and an antenna connected to theelectronic component; a pair of reinforcing pieces located respectivelyon the front and back surfaces of the sealing piece so as to sandwichthe electronic component, the reinforcing pieces being made of a firstmaterial harder than the elastic material; and a joint piece couplingthe reinforcing pieces to each other, the joint piece being made of asecond material harder than the elastic material.

The object and advantages of the embodiments will be realized andattained by means of the elements and combinations particularly pointedout in the appended claims. It is to be understood that both theforegoing general description and the following detailed description areexemplary and explanatory and are not restrictive of the embodiments, asclaimed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view schematically depicting a radio-frequencyidentification (RFID) tag according to a first embodiment;

FIG. 2 is a sectional view taken along the line 2-2 in FIG. 1;

FIG. 3 is a plan view schematically depicting the RFID tag of the firstembodiment;

FIG. 4 is a sectional view taken along the line 4-4 in FIG. 3;

FIG. 5 is a sectional view schematically depicting a process ofairtightly enclosing an inlet within a sealing piece;

FIG. 6 is a plan view schematically depicting a process of formingthrough holes in the sealing piece;

FIG. 7 is a sectional view schematically depicting a process ofattaching reinforcing pieces to the sealing piece;

FIG. 8 is a plan view schematically depicting an RFID tag according to asecond embodiment;

FIG. 9 is a sectional view taken along the line 9-9 in FIG. 8;

FIG. 10 is a perspective view schematically depicting an RFID tagaccording to a third embodiment;

FIG. 11 is a plan view schematically depicting the RFID tag of the thirdembodiment;

FIG. 12 is a side view schematically depicting the RFID tag of the thirdembodiment;

FIG. 13 is a perspective view schematically depicting a process ofcutting out the contour of the sealing piece;

FIG. 14 is a perspective view schematically depicting an RFID tagaccording to a fourth embodiment;

FIG. 15 is a plan view schematically depicting the RFID tag of thefourth embodiment;

FIG. 16 is a sectional view taken along the line 16-16 in FIG. 15;

FIG. 17 is a sectional view schematically depicting deformation of theRFID tag of the fourth embodiment;

FIG. 18 is a perspective view schematically depicting an RFID tagaccording to a fifth embodiment;

FIG. 19 is a side view taken along the line 19-19 in FIG. 18;

FIG. 20 is a sectional view schematically depicting deformation of theRFID tag of the fifth embodiment;

FIG. 21 is a sectional view schematically depicting a process of moldingthe reinforcing pieces and the joint pieces together in a mold;

FIG. 22 is a perspective view schematically depicting an RFID tagaccording to a sixth embodiment; and

FIG. 23 is a sectional view taken along the line 23-23 in FIG. 22.

DESCRIPTION OF EMBODIMENT

Embodiments of the present invention will be explained below withreference to the accompanying drawings.

FIG. 1 schematically depicts the exterior of a radio-frequencyidentification (RFID) tag 11 according to a first embodiment. The RFIDtag 11 includes a plate-shaped sealing piece 12, for example. Thesealing piece 12 has the shape of a flat parallelepiped, for example.The sealing piece 12 is made of an elastic material such as polyurethanerubber, for example. The sealing piece 12 thus has a predeterminedflexibility. A pair of reinforcing pieces 13 a, 13 b are located on thefront and back surfaces of the sealing piece 12, respectively. Thereinforcing pieces 13 a, 13 b are formed in the shape of a plate, forexample. The reinforcing pieces 13 a, 13 b have the shape of a flatparallelepiped, for example.

The reinforcing pieces 13 a, 13 b are made of a material harder than theelastic material of the sealing piece 12. Here, the reinforcing pieces13 a, 13 b are made of a fiber reinforced resin, for example. The fiberreinforced resin contains glass fibers impregnated with epoxy resin, forexample. Alternatively, the reinforcing pieces 13 a, 13 b may be made ofany one of resin materials such as polyphenylene sulfide (PPS) resin,polyether ether ketone (PEEK) resin, polyimide (PI) resin andpolyetherimide (PEI) resin.

As depicted in FIG. 2, an inlet 14 is airtightly enclosed within thesealing piece 12. The inlet 14 is interposed between a pair of thinplates 12 a, 12 b. The thin plates 12 a, 12 b in combination function asthe sealing piece 12. The thin plates 12 a, 12 b are bonded to eachother. The inlet 14 includes a base 16 of a thin plate. The base 16 iselongated in the longitudinal direction of the sealing piece 12. Thebase 16 is made of a resin material such as polyethylene terephthalate(PET), for example. An electronic component, namely a semiconductor chip17, is mounted on the surface of the base 16. An adhesive is utilized tofix the semiconductor chip 17 to the base 16, for example. Atransmitter/receiver circuit, logic circuit and a memory for radiocommunication are incorporated in the semiconductor chip 17, forexample. Predetermined information is held in the memory. Thesemiconductor chip 17 is made of silicon, for example.

An antenna device 18 is also mounted on the surface of the base 16. Theantenna device 18 include a pair of antenna wires 18 a, 18 b. Theantenna wires 18 a, 18 b in combination function as a dipole antenna.The antenna wires 18 a, 18 b are made of a copper (Cu) foil, forexample. Electrical connection is established between one ends of theantenna wires 18 a, 18 b and the semiconductor chip 17. The antennawires 18 a, 18 b extend linearly from the semiconductor chip 17 in theopposite directions to each other. Here, the antenna wires 18 a, 18 bare elongated in the longitudinal direction of the base 16. Electricpower is generated in the semiconductor chip 17 in response to radiowaves received at the antenna device 18. The semiconductor chip 17utilizes the electric power to execute a predetermined operation. Theinformation held in the memory is output from the antenna device 18, forexample.

The back surface of the reinforcing piece 13 a is overlaid on the frontsurface of the sealing piece 12. Likewise, the back surface of thereinforcing piece 13 b is overlaid on the back surface of the sealingpiece 12. The reinforcing pieces 13 a, 13 b have identical contours.Referring also to FIG. 3, the reinforcing pieces 13 a, 13 b are overlaidon projection image areas, respectively. The projection image areas aredefined along the projected images of the semiconductor chip 17 formedon the front and back surfaces of the sealing piece 12, respectively.Here, the projected image areas are defined inside the contours of thereinforcing pieces 13 a, 13 b. The contours of the reinforcing pieces 13a, 13 b extend larger than the projected image areas around theprojected image areas, respectively. The semiconductor chip 17 is inthis manner interposed between the reinforcing pieces 13 a, 13 b.

Joint pieces 19 are utilized to couple the reinforcing pieces 13 a, 13 bto each other, for example. The joint pieces 19 are arranged in two rowseach having three joint pieces 19, for example. The base 16, namely theinlet 14, is located between the rows of the joint pieces 19, forexample. The joint pieces 19 are made of a material harder than theelastic material of the sealing piece 12. Here, the joint pieces 19 andthe reinforcing pieces 13 a, 13 b are made of the same material. Theindividual joint piece 19 is formed in the shape of a column extendingin the direction of the thickness of the sealing piece 12, in otherwords, in the direction perpendicular to the front and back surfaces ofthe sealing piece 12, for example. Referring also to FIG. 4, the jointpieces 19 are received in through holes 21 each defining a columnarspace inside, for example. The through holes 21 penetrate from the frontsurface of the sealing piece 12 to the back surface of the sealing piece12. Here, the through holes 21 are located at positions outside thecontour of the inlet 14.

The RFID tag 11 is attached to clothes, for example. When the clothesare washed, the sealing piece 12 is bent as a result of twisting of theclothes. Bending stress is thus generated in the sealing piece 12. Thejoint pieces 19 are utilized to couple the reinforcing pieces 13 a, 13 bto each other. The reinforcing pieces 13 a, 13 b are thus allowed tohave a sufficient rigidity. Since the semiconductor chip 17 isinterposed between the reinforcing pieces 13 a, 13 b, generation ofstress is prevented in a space between the reinforcing pieces 13 a, 13b, namely at the semiconductor chip 17. This results in avoidance ofdamages to the semiconductor chip 17. Moreover, since the joint pieces19 are utilized to couple the reinforcing pieces 13 a, 13 b to eachother, a coating material is not required to cover the reinforcingpieces 13 a, 13 b on the front and back surfaces of the sealing piece12. An increase in the production cost of the RFID chip 11 can besuppressed. Simultaneously, the thickness of the RFID chip 11 can bereduced.

Next, description will be made on a method of making the RFID tag 11.Here, the inlet 14 is first prepared. As depicted in FIG. 5, the inlet14 is interposed between the thin plates 12 a, 12 b. Thermocompressionbonding is employed to bond the thin plates 12 a, 12 b to each other,for example. The inlet 14 is airtightly enclosed between the thin plates12 a, 12 b, namely within the sealing piece 12. As depicted in FIG. 6,the through holes 21 are formed in the sealing piece 12. The throughholes 21 penetrate from the front surface of the sealing piece 12 to theback surface of the sealing piece 12. The through holes 21 are formed atpositions outside the contour of the inlet 14. A punch may be employedto punch the sealing piece 12 to form the through holes 21, for example.

As depicted in FIG. 7, the reinforcing piece 13 b is overlaid on theback surface of the sealing piece 12 at a predetermined position. Oneends of the joint pieces 19 have been bonded to the reinforcing piece 13a, for example. The joint pieces 19 are inserted in the through holes21, respectively. The reinforcing piece 13 a is overlaid on the frontsurface of the sealing piece 12. The other ends of the joint pieces 19are bonded to the reinforcing piece 13 b. Application of an adhesive ora heat welding technique may be utilized to bond the joint pieces 19 tothe reinforcing pieces 13 a, 13 b, for example. The RFID tag 11 is inthis manner produced. It should be noted that the joint pieces 19 may beformed integral with the reinforcing piece 13 a based on molding, forexample.

The method allows establishment of the through holes 21 in the sealingpiece 12 prior to the attachment of the reinforcing pieces 13 a, 13 b.The joint pieces 19 have beforehand been bonded to the reinforcing piece13 a. The insertion of the joint pieces into the respective throughholes 21 enables an easier positioning of the reinforcing piece 13 arelative to the sealing piece 12, specifically the semiconductor chip17. The through holes 21 are formed at accurate positions relative tothe semiconductor chip 17 by using a punch, for example. Therefore, thereinforcing piece 13 a is positioned relative to the semiconductor chip17 with accuracy in a facilitated manner. Likewise, the reinforcingpiece 13 b is positioned relative to the joint pieces 19 in afacilitated manner. The reinforcing piece 13 b is positioned relative tothe semiconductor chip 17 with accuracy.

FIG. 8 schematically depicts an RFID tag 11 a according to a secondembodiment. The RFID tag 11 a is configured to employ the joint pieces19 each made of a single wall or block. The joint piece 19 has thecontour of a flat parallelepiped, for example. Referring also to FIG. 9,the joint pieces 19 are received in the through holes 21, respectively.The through holes 21 are located at positions outside the contour of theinlet 14. Like reference numerals are attached to the structure orcomponents equivalent to those of the aforementioned RFID tag 11. TheRFID tag 11 a is allowed to enjoy the advantages identical to thoseobtained in the aforementioned RFID tag 11. The RFID tag 11 a isproduced in the same manner as the aforementioned RFID tag 11.

FIG. 10 schematically depicts an RFID tag 11 b according to a thirdembodiment. A constriction 25 is formed in the sealing piece 12 of theRFID tag 11 b between enlarged end portions. The constriction 25 isconfigured to describe recessed contours 25 a, 25 a of the sealing piece12. The recessed contours 25 a, 25 a are recessed inward from arectangular shape matched with the enlarged end portions 12 c, 12 c ofthe sealing piece 12. Referring also to FIG. 11, the constriction 25 maybecome narrower as the position gets farther from the enlarged endportions 12 c, 12 c of the sealing piece 12, for example. The recessedcontours 25 a, 25 a include lines extending in parallel with thelongitudinal edges of the base 16, respectively, so as to define thenarrowest portion. Referring also to FIG. 12, the joint pieces 19 arereceived in the recessed contours 25 a, 25 a. The individual joint piece19 is a single wall, for example. The constriction 25 is interposedbetween the joint pieces 19, 19. As a result, the reinforcing pieces 13a, 13 b and the joint pieces 19 surrounds the constriction 25. Thereinforcing pieces 13 a, 13 b and the joint pieces 19 are thus preventedfrom dropping off the sealing piece 12. Like reference numerals areattached to the structure or components equivalent to those of theaforementioned RFID tags 11, 11 a. The RFID tag 11 b is allowed to enjoythe advantages identical to those obtained in the aforementioned RFIDtag 11 a.

Next, description will be made on a method of making the RFID tag 11 b.The inlet 14 is airtightly enclosed between the thin plates 12 a, 12 bbased on thermocompression bonding, for example, in the same manner asdescribed above. The contours of the thin plates 12 a, 12 b at thisstage are larger than those of the thin plates 12 a, 12 b for a finalproduct. As depicted in FIG. 13, a cutter 26 is used to cut out thecontour of the sealing piece 12. The cutter 26 defines the contour ofthe sealing piece 12. In this manner, the constriction 25 is formed inthe contour of the sealing piece 12. The reinforcing piece 13 b is thenlocated on the back surface of the sealing piece 12 in the same manneras described above. One ends of the joint pieces 19 have beforehand beenbonded to the reinforcing piece 13 a. The joint pieces 19 are receivedin spaces of the recessed contours 25 a, 25 a, respectively. The otherends of the joint pieces 19 are bonded to the reinforcing piece 13 b.The RFID tag 11 b is in this manner produced. The method enablesreception of the joint pieces 19 in the recessed contours 25 a, 25 a foran easier positioning of the reinforcing pieces 13 a, 13 b relative tothe semiconductor chip 17.

FIG. 14 schematically depicts an RFID tag 11 c according to a fourthembodiment. The RFID tag 11 c includes a pair of recesses 27, 27 formedin the reinforcing pieces 13 a, 13 b of the aforementioned RFID tag 11b. Referring also to FIG. 15, the recesses 27 are configured to describerecessed contours of the reinforcing piece 13 a(13 b) and to intersectthe antenna wire 18 a(18 b). Specifically, the recesses 27 are recessedin the direction of the antenna wire 18 a(18 b). The recesses 27, 27become narrower as the position gets farther from the correspondingenlarged end portions 12 c, 12 c, for example. Referring also to FIG.16, the inner peripheries of the recesses 27 are defined withinperpendicular planes standing upright from the front and back surfacesof the sealing piece 12. Like reference numerals are attached to thestructure or components equivalent to those of the aforementioned RFIDtag 11 b.

When the clothes are washed, the sealing piece 12 of the RFID tag 11 cis bent as a result of twisting of the clothes, as depicted in FIG. 17.The antenna wires 18 a, 18 b are forced to bend. The sealing piece 12 isforced to bend around the side edges of the reinforcing pieces 13 a, 13b at positions outside the recesses 27. The sealing piece 12 suffersfrom bending stress concentrated on the side edges of the reinforcingpieces 13 a, 13 b. Even in such a situation, since the sealing piece 12is made of an elastic material such as polyurethane rubber, damages tothe sealing piece 12 are avoided. The recesses 27 are configured todescribe the recessed contours of the reinforcing pieces 13 a, 13 b inthe direction interesting the antenna wire 18 a(18 b). As a result, thesealing piece 12 is prevented from contacting with the side edges of thereinforcing pieces 13 a, 13 b. Concentration of the bending stress isavoided. Tight bending of the antenna wires 18 a, 18 b is restricted.This results in avoidance of breaking of the antenna wires 18 a, 18 b.The reinforcing pieces 13 a, 13 b are still allowed to extend over arelatively wide area irrespective of the formation of the recesses 27.The reinforcing pieces 13 a, 13 b are thus allowed to have a sufficientrigidity. Generation of the stress is reliably suppressed in the sealingpiece 12 at a position adjacent to the semiconductor chip 17.

FIG. 18 schematically depicts an RFID tag 11 d according to a fifthembodiment. The RFID tag 11 d includes rounded edges formed in thereinforcing pieces 13 a, 13 b of the aforementioned RFID tag 11 b.Referring also to FIG. 19, the rounded edges of the reinforcing pieces13 a, 13 b extend in a direction intersecting the antenna wires 18 a, 18b at right angles so as to define the contour of the reinforcing pieces13 a, 13 b. Here, curved surfaces are defined at the side edges of thereinforcing pieces 13 a, 13 b. The curved surfaces are configured tohave generatrices extending in parallel with the center axes Xintersecting the antenna wires 18 a, 18 b, respectively, at rightangles. The individual center axis X is equally spaced from the frontand back surfaces of the reinforcing piece 13 a(13 b). Like referencenumerals are attached to the structure or components equivalent to thoseof the aforementioned RFID tag 11 b.

When the clothes are washed, the sealing piece 12 of the RFID tag 11 dis forced to bend as a result of twisting of the clothes. The antennawires 18 a, 18 b are thus forced to bend. The rounded edges are formedas the side edges of the reinforcing pieces 13 a, 13 b extending in thedirection intersecting the antenna wires 18 a, 18 b at right angles.Consequently, the antenna wires 18 a, 18 b are forced to bend along thecurved surfaces, as depicted in FIG. 20.

Tight bending of the antenna wires 18 a, 18 b is restricted. Thisresults in avoidance of breaking of the antenna wires 18 a, 18 b. Thereinforcing pieces 13 a, 13 b are still allowed to extend on the frontand back surfaces of the sealing piece 12 over a relatively large area.The reinforcing pieces 13 a, 13 b are thus allowed to have a sufficientrigidity. Generation of the stress is reliably suppressed in the sealingpiece 12 at a position adjacent to the semiconductor chip 17.

Next, description will be made on a method of making the RFID tag 11 d.The inlet 14 is airtightly enclosed between the thin plates 12 a, 12 bbased on thermocompression bonding, for example, in the same manner asdescribed above. The thin plates 12 a, 12 b, namely the sealing piece12, are set in a cavity 29 of a mold 28, made of a metal material, asdepicted in FIG. 21. The mold 28 includes a first mold 28 a and a secondmold 28 b. The first mold 28 a and the second mold 28 b are coupled toeach other at a coupling surface extending in the directionperpendicular to the front and back surfaces of the sealing piece 12. Aspace is defined in the cavity 29 at a position outside the sealingpiece 12. The space defines the externals or contours of the reinforcingpieces 13 a, 13 b and the joint pieces 19. Predetermined blocks arenested in the cavity 29 to form such a space. The aforementioned resinmaterial is poured into the space. When the resin material is hardenedor cured, the reinforcing pieces 13 a, 13 b and the joint pieces 19 areformed. The RFID tad 11 d is in this manner produced.

FIG. 22 schematically depicts an RFID tag 11 e according to a sixthembodiment. The RFID tag 11 e includes rounded edges formed in thereinforcing pieces 13 a, 13 b inside the recesses 27, 27 of theaforementioned RFID tag 11 c. The rounded edges inside the recesses 27,27 extend in a direction intersecting the antenna wires 18 a, 18 b atright angles so as to define the contour of the reinforcing pieces 13 a,13 b. Referring also to FIG. 23, curved surfaces are configured to havegeneratrices extending in parallel with the center axes X intersectingthe antenna wires 18 a, 18 b, respectively, at right angles. Theindividual center axis X is equally spaced from the front and backsurfaces of the reinforcing piece 13 a(13 b). Like reference numeralsare attached to the structure or components equivalent to those of theaforementioned RFID tag 11 c. The RFID tag 11 e is allowed to enjoy theadvantages identical to those obtained in the aforementioned RFID tags11 c, 11 d.

The recesses 27, 27 may be formed in the reinforcing pieces 13 a, 13 bof any one of the aforementioned RFID tags 11, 11 a. Likewise, therounded edges may be formed in the reinforcing pieces 13 a, 13 b of anyone of the aforementioned RFID tags 11, 11 a. The sealing piece 12, thereinforcing pieces 13 a, 13 b, the joint pieces 19, the constriction 25and the recesses 27 can take any shape or form different from thedescribed ones. Molding process may be employed to form the reinforcingpieces 13 a, 13 b and the joint pieces 19 in the RFID tags 11, 11 a, 11b, 11 c in the same manner as in the RFID tag 11 d.

All examples and conditional language recited herein are intended forpedagogical purposes to aid the reader in understanding the inventionand the concept contributed by the inventor to furthering the art, andare to be construed as being without limitation to such specificallyrecited examples and conditions, nor does the organization of suchexamples in the specification relate to a showing of the superiority andinferiority of the invention. Although the embodiments of the presentinventions have been described in detail, it should be understood thatthe various changes, substitutions, and alterations could be made heretowithout departing from the spirit and scope of the invention.

1. A radio-frequency identification tag comprising: a plate-shapedsealing piece made of an elastic material; an inlet enclosed within thesealing piece, the inlet including an electronic component and anantenna connected to the electronic component; a pair of reinforcingpieces located respectively on front and back surfaces of the sealingpiece so as to sandwich the electronic component, the reinforcing piecesbeing made of a first material harder than the elastic material; and ajoint piece coupling the reinforcing pieces to each other, the jointpiece being made of a second material harder than the elastic material.2. The radio-frequency identification tag according to claim 1, furthercomprising a through hole penetrating from the front surface of thesealing piece to the back surface of the sealing piece, the through holereceiving the joint piece therein.
 3. The radio-frequency identificationtag according to claim 1, further comprising a constriction formed inthe sealing piece, the constriction describing a recessed contour of thesealing piece for receiving the joint piece.
 4. The radio-frequencyidentification tag according to claim 1, further comprising recessesformed in the reinforcing pieces, the recesses describing recessedcontours of the reinforcing pieces and extending across the antenna. 5.The radio-frequency identification tag according to claim 1, wherein thereinforcing pieces has rounded edges extending in a directionintersecting across the antenna so as to define a contour of thereinforcing pieces.